Method of regulation of the duration of repeated rectangular electric signal and devices for the practical application of the same method

ABSTRACT

Method and apparatus are disclosed for varying the width of a rectangular pulse which controls the opening of an electromagnetic fuel injector, in accordance with engine speed. Reference pulses of short duration are generated in synchronism with engine rotation and these pulses are utilized to generate injection pulses, and control pulses. The termination of the control pulse, which is of predetermined width, is utilized to generate a linearly increasing reference voltage which reaches a predetermined voltage level, depending on the spacing between the preceding reference pulse and the following reference pulse. The voltage level reached by the reference voltage is utilized to cut off the injection pulse. The width of the injection pulse, and in consequence the quantity of fuel injected, is thus directly controlled by engine speed, i.e., by the spacing of the reference pulses.

United States Patent Monpetit Mar. 21, 1972 54] METHOD OF REGULATION OF THE 3,051,152 8/1962 Paule et al. ..123/119 DURATION OF REPEATED 1 3,338,221 8/1967 Scholl ..l23/ll9 RECTANGULAR ELECTRIC SIGNAL AND DEVICES FOR THE PRACTICAL APPLICATION OF THE SAME METHOD Louis A. Monpetit, Etang-la-Ville, France Societe des Procedes Modernes dlnjection Sopromi, Les Mureaux, France Sept. 20, 1968 lnventor:

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data Sept. 25, 1967 France ..72224l U.S. Cl ..307/265, 123/119, 328/58 Int. Cl. ..H03k 5/04 Field of Search "123/1 19; 307/265, 266, 267; 328/58 References Cited UNITED STATES PATENTS 1 Primary Examiner-Donald D. Forrer Assistant ExaminerR. C. Woodbridge Attorney-Kenyon Kenyon Reilly Carr & Chapin ABSTRACT Method and apparatus are disclosed for varying the width of a rectangular pulse which controls the opening of an elecf tromagnetic fuel injector, in accordance with engine speed.

Reference pulses of short duration are generated in 1 synchronism with engine rotation and these pulses are utilized to generate injection pulses, and control pulses. The termination of the control pulse, which is of predetermined width, is

utilized to generate a linearly increasing reference voltage which reaches a predetermined voltage level, depending on the spacing between the preceding reference pulse and the following refer'ence pulse. The voltage level reached by the reference voltage is utilized to cut off the injection pulse. The width of the injection pulse, and in consequence the quantity of fuel injected, is thus directly controlled by engine speed, i.e., by the spacing of the reference pulses.

9 Claims, 1 1 Drawing Figures PATENTEUMARZI I972 3, 651 ,343

SHEET 1 UF 5 A 0 0/: Mow: r/r

PATENTEDM'ARZI I972 SHEET 3 BF 5 W A. A. ll. 7 :J i fid a 1 6'1 c Q 'U m U w W 10 R IF II. #8 I m m m U aaaa JLMJL PATENTEDMARZ] I972 sum 5 OF 5 J MM P: 7'/ r METHOD OF REGULATION OF THE DURATION OF REPEATED RECTANGULAR ELECTRIC SIGNAL AND DEVICES FOR THE PRACTICAL APPLICATION OF THE SAME METHOD The present invention relates to a method of regulation of the duration of a repeated rectangular electric signal, the duration of said rectangular signal being regulated as a function of the repetition time. Said method is applicable in particular to the regulation of the injection time of electromechanical injectors or transducers which are controlled by said rectangular signal as a function of speed of rotation in internal combustion engines. The invention is also concerned with devices for carrying out said method.

In some electronic injection systems, the quantity of fuel injected per cycle is a simple and usually linear function of the duration of a voltage signal which is applied to an injector or transducer. In the case, for example, of overspeed regulation, it accordingly follows that the regulation of injection entails the maintenance of a constant duration of the electric signal at any speed below a predetermined limit, above which said duration is progressively reduced to a sufficiently small value which, at a given moment, is such that the quantity injected is reduced to zero.

order to obtain a regulation-of this type, it is known to make use of devices for producing a voltage which is a function of the engine speed. This voltage can be supplied, for exwith the electronic injection-control system. The device referred-to makes it possible to obtain a voltage which increases with the speed of rotation of the engine and the integration of the signals which initiate the commencement of the injection is carried out by suitable electronic means.

However, in the case of known devices, it is necessary to transform a voltage which increases with the speed of rotation into a voltage which decreases with over-speed in order to reduce the time-duration of injections. In addition, the voltage variation is small in respect of small variations in the speed of rotation, the precision of regulation being consequently affected.

The object of the present invention is to circumvent the disadvantages noted above and is therefore intended to provide A method of regulation of the duration of a repeated rectangular electric control signal, characterized in that a signal corresponding to the beginning of the first rectangular signal of the series of control signals initiates a rectangular reference signal of externally variable duration, the end of said reference signal being utilized to initiate a variation of a regulation voltage, said regulation voltage being utilized to vary following the end of a rectangular control signal in order to modify the duration thereof.

A device for the practical application of the method in accordance with paragraph a) hereinabove, characterized in that said device comprises a first flip-flop having two transistors and a timing element having a variable resistor, a capacitor and a unijunction transistor, said first flip-flop having a first input for the signal which releases the rectangular control signal and a second input for the signal corresponding to the end of the rectangular control signal and coupled with the timing element that said device further comprises a second flip-flop having two transistors and a timing element with a variable resistor, a capacitor and a unijunction transistor, said second flipflop having a first input for the signal which releases the rectangular reference signal induced by the beginning of a given rectangular control signal and a second input for the signal corresponding to the end of the rectangular reference signal and coupled with the timing element of said second flip-flop that said device further comprises a device for producing a variation in the regulation voltage which is applied to the base of the unijunction transistor of the first flip-flop, said device being made up of a first capacitor which is charged from a voltage source through a diode and a variable resistor, the terminal voltage of said first capacitor being applied to the base of a transistor whose collector is connected to a voltage source and whose emitter is connected to a second capacitor as well as to the base of the unijunction transistor of the first flip-flop through a diode and a resistor, a voltage which can be varied by means of a voltage divider and which is either lower than or equal to the I regulation voltage being also applied via a diode to the base of the unijunction transistor of the first flip-flop, the charge on the first capacitor being controlled by a device constituted by a transistor whose base is connected to the output of the second flip-flop and whose emitter is connected to ground whilst the collector is connected to the supply of said first capacitor upstream of the diode so that when said charge-control transistor is saturated, no supply voltage is applied any longer to said first capacitor, said first capacitor being discharged at the end of each rectangular control signal by means of a signal delivered by the timing element of the first flip-flop and applied to a first transistor which in turn drives a second transistor into saturation through a resistor and a capacitor, the emitter of said second transistor being connected to ground and the collector being connected to the terminal of said first capacitor through a resistor and a diode.

The invention additionally comprises all or a part of the characteristics mentioned hereinafter and considered either separately or in combination. Reference is made to the accompanying drawings which are given by way of example in order that the description may be more readily understood, and in which FIG. 1 is a simple example of the progressive variation of the regulation voltage as a function of the recurrence time FIG. 2 is a representation of the different electric signals which are produced in order to obtain a regulation in ac cordance with the invention FIG. 3 is a block diagram of a regulation device in accordance with a first embodiment FIG. 4 is a detailed circuit diagram of a regulation device in accordance with a first embodiment FIG. 5 is a representation of the different electric signals which are produced in order to obtain a regulation in accordance with another embodiment FIG. 6 is a block diagram of a device for obtaining a regulation in accordance with FIG. 5

FIG. 7 is a detailed circuit diagram of an element to be inserted in the diagram of FIG. 4 in order to obtain a regulation according to FIG. 5

FIG. 8 is an example of progressive variation of the regulation voltage as a function of the recurrence time in the case of an engine with controlled ignition FIG. 9 is a representation of some of the electric signals which are produced in order to obtain a regulation according to FIG. 8

FIG; 10 is a block diagram of a device for obtaining a regulation according to FIG. 8

FIG. 11 is a detailed and complete circuit diagram for obtaining a regulation according to FIG. 8.

Referring to FIG. 1 there is shown the fuel injection characteristic for a constant-speed Diesel engine. The quantity of fuel 0 which is injected during each cycle is proportional to the injection time T and to the regulation voltage V and does not vary in the case of a speed of rotation which is lower than N,, (as shown in FIG. I). Said speed N is a reference value for the regulation of fuel injection. If for any reason the speed of rotation becomes higher than N the injection is progressively decreased with a certain static stability of regulation which is defined by the difference between the speed N, at which the injection becomes zero and the reference value N In FIG. 2, there are shown at (I) the signals for triggering the injection having a repetition period T,,. These signals are derived from a pulse emitter ILS (FIG. 3) with flexible-blade switches, for example, said emitter being driven in rotation by the motor M (FIG. 3), and are directed into a device A. There are shown at (II) in FIG. 2 the rectangular signals which control the injection time T, and which also have a repetition period T,. The beginning a of the signal is synchronous with the speed of rotation whilst the end b is varied in accordance with engine speed. At the time a of triggering of an injection, an electronic device B changes from a state to a state 01 (line III, FIG. 2) and returns to state 00 at the point marked c at the end of a time T which can be varied externally. At the time c, a device E receives a signal and the regulation voltage begins to vary progressively, this variation being represented in the present instance by the terminal voltage of a capacitor which is charged through a resistor. Said regulation voltage changes in a time T, from a variable value V, to a maximum value V as represented by the point d of line IV in FIG. 2 if the time interval T between two subsequent injections is longer than the added time intervals T T,,Said voltage retains this value until the end b of the second injection and is caused to revert to the value V,, by a signal which is transmitted to the device E from the device A at the end of said injection. If, on the contrary, the time interval (T; FIG. 2 line I, between two subsequent injections is shorter than the added time intervals (T, T the voltage rise is stopped at the value V n by a signal derived from the device D and corresponding to the beginning of the following injection and the reduced regulation voltage accordingly acts on the device A so as to cutoff the injection at b.

As a result of this arrangement, the value of the regulation voltage is located and stabilized at the beginning of an injection at a value which is comprised between V (variable) and V In the case of a given value of T and of T,, said value is equal to V if T is than T, T,, that is to say if the speed of rotation of the engine is lower than a reference value. If I, becomes shorter, that is to say if the speed increases, the value of the regulation voltage will decrease from the moment when T, T,, T, and will drop from V to V when (T,,) equals (l that, if the value of the regulation voltage is employed at the moment of triggering of the injection so as to control the duration of this latter, the quantity of fuel will change from the value corresponding to V to that which corresponds to V in respect of a variation in the engine period equal to T, which is as small as may be desired.

There is shown in FIG. 4 one non-limitative example of arrangement of an electronic circuit which carries out a regulation of the injection time according to FIGS. 1 to 3. The assembly A is constituted by a flip-flop formed by two transistors T,, T, and the resistors R,, R R R, and a timing element constituted by a relaxation oscillator which acts on the input E of said flip-flop and comprises a unijunction transistor U,, a capacitor C, and a variable resistor R,. A negative pulse applied to the input E, of the flip-flop causes the appearance of a rectangular signal having a duration T, at the output 8,. The output S, is coupled with the input E of an assembly B via the diode D the capacitor C and the resistor R, and the diode D,, and the resistor R have the function of discharging the capacitor after the passage of a pulse. The assembly B is also a flip-flop which is similar to that in A. Said flip-flop is made up of the transistors T T and the resistors R R,,, R,,,, R R R and a timing element which produces action on the input E of said flip-flop with a unijunction transistor U a capacitor C and a variable resistor P in series with a diode D and a resistor R A positive pulse applied to the input E causes the appearance of a rectangular signal having a duration T at the output S Said output 5, is connected to an assembly D which controls the increase in the voltage V,,. Said assembly D is constituted by the resistors R R R and the transistor T,,,

said transistor being saturated during the time T of the signal at the output S of the second flip-flop. Said assembly D which serves to control the voltage rise iscoupled with the assembly E via the diode D The assembly D comprises a first portion which has the function of increasing the regulation voltage V,, and transmitting this latter to the unijunction transistor of the assembly A. Said first portion is constituted by the capacitor which is charged from the resistor R through the variable resistor P The voltage V which is developed across the terminals of the capacitor C is applied to the base of the transistor T, via the resistor R,, The base regulation voltage V is taken from the voltage divider P, and transmitted via the diode D to the base 2 of the unijunction transistor U,, the voltage V,, is delivered from the transistor T via the diode (D and the resistor R and corresponds to the terminal voltage of the capacitor (C,) which is dependent on the voltage V which is applied to the base of the transistor T The second portion of the assembly D carries out the discharge of the capacitor C, at the end of each injection having a duration T,. To this end, a transistor T, is connected at its base to the input E of the first flip-flop in the assembly A, the emitter of said transistor being connected to ground and the collector being connected to the base of a transistor T through a resistor R and a capacitor C as well as to a voltage source through the resistor R The emitter of the transistor T is connected to ground and its collector is connected to the terminal of the capacitor C through the diode D, and the resistor R Finally, a resistor R is connected to the base of the transistor T and the capacitor C is connected to ground. In order to prevent any troublesome occurrences at the time of a sudden reduction in the time T, when modifying the variable resistor P in the assembly B, provision is accordingly made for an assembly F consisting of a transistor T the collector of which is connected to the capacitor C; through the resistor R and the emitter of which is connected to ground. Said transistor is saturated at the beginning of each injection by a signal which is transmitted from the output S, of the assembly A via the diode D the resistor R and the capacitor C to the base of said transistor I the resistors R and R being intended to discharge the capacitor C The operation of the device is as follows:

A negative pulse which is applied to the input E, of the assembly A initiates a change of state and the appearance of the rectangular signal for controlling the injection having a duration T, at .the output 8,. This pulse is transmitted to the input E of the assembly B and initiates a change of state and the appearance of the rectangular reference signal having a duration T at the output S The same pulse at S, is also transmitted to the base of the transistor T thereby driving said transistor into saturation for a very short time, with the result that the capacitor C can discharge. This is carried out in order to ensure that said capacitor C is fully discharged as each cycle of operation begins again. The signal which appears at the output 8, of the assembly B is applied to the base of the transistor T, and drives this latter into saturation. As a result, the point of connection of the diode D and resistor R is grounded and no charge voltage is therefore applied any longer to the tenninals of the capacitor C and this latter accordingly remains at the voltage V which it had reached at the moment of saturation of the transistor T The voltage V,,, is applied to the base of the transistor T with the result that the capacitor C, is charged to a regulation voltage V which is dependent on the voltage V which is developed across the terminals of the capacitor C The regulation voltage V is applied to the base 2 of the unijunction transistor U, and initiates a reversal of state of the assembly A when the terminal voltage of the capacitor (C,) is approximately equal to the regulation voltage V thereby turning transistor T on and causing the appearance of a positive signal at the input E of the flip-flop. At the end of the injection, the signal produced at the input E is transmitted to the device for discharging the capacitor C, which device is constituted by the transistors T, and T, which, being saturated by the end-of-injection pulse, through the resistor R permit the discharge of said capacitor C The capacitor C, then discharges at a slower rate through the unijunction transistor U until the voltage V which is obtained from the voltage divider P is reached. The assembly B changes state again at the end of a time T,, which is determined in a similar manner by the timing element U C P and the transistor T changes to the blocked state so that the capacitor C begins to charge again at a rate which is dependent on the resistor P.,. If the following injection occurs at the end of a time interval T which is longer than the added time intervals T, T,, the capacitor C will be fully charged to the maximum voltage and the duration of the injection corresponds to the application of the maximum voltage V to the base 2 of the unijunction transistor U and there is no decrease in the quantity of fuel injected.

On the other hand, if the subsequent injection occurs at the end of a time interval T; which is shorter than the added time intervals T, T,, the charge on the capacitor C is stopped at a lower value owing to the saturation of the transistor T and a regulation voltage V which is lower than the maximum voltage V is applied to the base 2 of the unijunction transistor U and, as a consequence, the injection time is reduced in proportion.

Should it not be desired to initiate the formation of the regulation voltage V at each injection, for example in the event that the injections to be carried out are not uniformly spaced as is occasionally the case with some types of V-engines, it is possible to employ for the purpose of forming said regulation voltage V only a part of the injection trigger signals or even one of these latter, and in fact one or a number of independent pulse emitters ILS ILS which are coupled, for example, with the camshaft of the engine M.

In this case, two successive pulses a for producing the regulation voltage V are separated by the time interval corresponding to two engine revolutions or only one revolution if the pulse emitter is coupled with the crankshaft and not with the camshaft.

The principle of formation of the voltage then remains substantially the same. A value To is assigned to a flip-flop B which is triggered by said pulse emitter ILS and an injection flip-flop A is triggered by the pulse emitter ILS A regulation voltage V is then formed as in the previous instance and will be stored from one engine revolution to the next in order to ensure regulation.

In FIG. 5, there is accordingly shown the voltage diagram in which line I represents the usual injection'pulses,

line I represents the articular regulation forming pulses,

line II represents the injection signals corresponding to the time interval T line Ill represents the reference signal having the duration line IV represents the regulation voltage formed by the two above-mentioned devices in accordance with the process which has been explained earlier and line V represents the value of the stored regulation voltage It is thus possible to employ a device as shown in FIGS. 3 and 4, with the modifications indicated in FIGS. 6 and 7 the output S of the assembly A is no longer connected either to the input E of the assembly B or to the assembly F. In this case, the triggering operation will be carried out by a pulse emitter ILS, as shown in FIG. 6. Provision must also be made for a storage device which is connected between one terminal of the capacitor C in FIG. 4 and the base of the transistor T This circuit shown in FIG. 7 is constituted by a first transistor T the base of which is supplied through a resistor R at the value of voltage V which is reached by the capacitor C As a result, the capacitor C is charged in proportion to said voltage V by said transistor T through the resistor R and the diode D,,. A second transistor T is also provided for the purpose of discharging the capacitor C through the resistor R when the voltage V is lower than that which is stored in the capacitor C The voltage of the output S of the assembly A is accordingly applied to the base of the second transistor T through a resistor R The method and devices hereinabove described are primarily employed with Diesel engines but it is apparent that they also have application to gasoline engines. In this case, however, it is sometimes useful to endow the regulation voltage with a more complex waveform as shown in FIG. 8. From this figure, it is apparent that in the case of a short time interval T that is to say in the case of a high speed of rotation, the regulation voltage V decreases from the maximum value V to the value V and that in the case of a long time interval T that is to say with a low speed of rotation, the regulation voltage V also decreases from the maximum value V to an intermediate value V The signals employed then have the waveform shown in FIG. 9. The signal shown in line Illa of the figure is formed in an assembly C and the signal of line IIIb is formed in the assembly D of FIG. 10. The signals of assemblies A and B remain the same. The regulation voltage V, formed in the assembly E then has the waveform shown in line IV. The voltage rises between the points 0 and d and is maintained up to point e, then falls between points e and f down to the level stage f b. At b, the voltage V drops to the value Vo.

Referring now to FIGS. 10 and 11, the injection control device is accordingly constituted in one non-limitative example of construction by an assembly A for setting up T, which is formed by a flip-flop with two transistors T T the resistors R,, R R R R R R R and the capacitors C and C as well as by the timing element with the unijunction transistor [1,, the capacitor C and the variable resistor P The assembly B which sets up To is connected at its input E to the assembly 7 A and is triggered at the same time as this latter. The assembly B comprises another flip-flop with the two transistors T T its resistors R R R R R and its timing element formed by the unijunction transistor U the capacitor C the variable resistor P and the resistor R Another assembly C which sets up To, is coupled with its input E, to the assembly B through a capacitor C Said assembly C being made up of a third flipflop with its two transistors T T its resistors R R R R R R and its timing element formed by the unijunction transistor U the capacitor C the variable resistor P and the fixed resistors R R The assembly C is additionally coupled with its input E to the output S of the assembly A through the diode D Finally the input E of a fourth assembly D is connected to the assembly C through the capacitor C and the input E, is connected to the output S of the assembly A through the diodes D and D Said assembly D is formed by a fourth flip-flop with its two transistors T 2, T and its resistors R R R R R R R The output 8, of said assembly B drives the base of the transistor "l through the resistor R The assembly E corresponds to that of FIG. 4 it is composed of the capacitor C;, which is charged from the output S of the assembly C through a diode D a variable resistor R, and a resistor R,, Said capacitor C can be discharged through the variable resistor R, and the transistor T when this latter is saturated but is also discharged through the resistor R and the transistor T when this latter is saturated by a pulse derived from the transistor T via the capacitor C and the resistor R the base of the said transistor T being connected to the input E of the assembly A. The supply voltage is applied to the collectors of the transistors T T via the resistors R R and to 'a voltage divider P;, which supplies the voltage V0 to the base 2 of the unijunction transistor U via the diode D The voltage developed across the terminals of the capacitor C is applied to the base of the transistor T via a resistor R Said voltage again has the form of a regulation voltage V at the terminals of the capacitor C, which is charged by the transistor T through the resistor R The voltage V,, is also transmitted to the base 2 of the unijunction transistor U via the resistor R Finally, the assembly F serves to discharge the capacitor C of the assembly B and the capacitor C of the assembly C through the diodes D D the resistor R and the transistor T; when this latter is saturated IOIOZB 0549 for a short time by a pulse derived from the output S of the assembly A via the capacitor C and the resistor R The resistor R serves to discharge the capacitor C The operation is accordingly as follows the pulse applied to the input E triggers the assembly A for a period T, and triggers the assembly B via the input E for a period To. The end of the signal of assembly B is transmitted to the assembly C via the input E and triggers this latter for a period T0,. At this moment, the capacitor C of the assembly E is charged through the transistor T of assembly C. The charge is stopped when assembly C again changes state, namely either at the end of a time interval To, which corresponds to the relaxation time of its timing element or at the beginning of the following injection by means of a signal which is derived from the output 8, of assembly A and transmitted to the input E of assembly C. A reversal of state of assembly C has the effect of triggering assembly D through the input E thereby saturating the transistor T which is connected to the output S of assembly D and the capacitor C discharges at a predetermined rate through the resistor P and said transistor T The discharge isstopped at the beginning of the following injection by a reversal of state of assembly D which is initiated in the case of the injection-commencement signal which is transmitted from the output S of assembly A to the input E of assembly D. Full discharge is carried out as in the previous instance by the injection-completion pulse from the input E of the assembly and the transistors T T The result achieved by this arrangement is that, when the time interval T is shorter than the added time intervals To I the duration of the injection is progressively decreased to zero and that, when the time interval le is longer than the added time intervals To T0,, the duration of the injection is also reduced, in proportion, to a predetermined value corresponding to the voltage (V of the level stage f-b.

It is readily understood that the invention is not limited to the exemplified embodiments hereinabove described but that the method can be employed with other equivalent electronic circuits. It is apparent in particular that the progressive variation of the regulation voltage V could take place either upwards or downwards in order to obtain a variation of the injection time.

What is claimed is:

l. A method of controlling the width of a rectangular pulse in response to a series of reference pulses of variable spacing, comprising the steps of:

a. generating a first pulse of variable width commencing with a pulse in said series of reference pulses;

b. generating a rectangular control pulse of predetermined duration commencing with said pulse in said series of reference pulses;

c. generating a reference voltage, the voltage level of which is dependent upon the spacing of said reference pulses in comparison to the duration of said control pulse; and

d. modifying the duration of said first pulse as a function of the voltage level of said reference voltage.

2. The method set forth in claim 1 wherein said reference voltage is generated in response to the termination of said control pulse.

3. The method set forth in claim 2 wherein said reference voltage is generated from an initial level, linearly up to a predetermined maximum level when the spacing of said reference pulses bears a predetermined relationship to the width of said control pulse and up to a value lower than said 5 predetermined maximum level when the spacing of said reference pulses varies from said predetermined relationship.

4. The method set forth in claim 3 including the further step of returning said reference voltage to said initial level in response to the termination of a second pulse of variable width 10 generated after said first pulse.

5. The method set forth in claim 1 wherein the duration of said rectangular control pulse is greater than the spacing between two pulses in said series of reference pulses and further including the step of storing said reference voltage for modifying the duration of at least two pulses of variablewidth. 6. he method set forth in claim 1 further mcludmg the steps of:

a. generating a second rectangular control pulse of predetermined duration in response to the termination of said first rectangular control pulse;

b. modifying the voltage level of said reference voltage in accordance with the duration of said second rectangular control pulse; and

c. modifying the duration of said first pulse of variable width in accordance with the modification in said voltage level when the spacing between two reference pulses exceeds the pulse widths of said first and second rectangular control pulses.

7. A circuit for modifying the width of a rectangular pulse in response to a series of reference pulses of variable spacing, comprising:

a. means responsive to a reference pulse in said series of reference pulses for generating a first pulse of variable width;

b. means for generating a rectangular control pulse of predetermined duration at the same time said first pulse of variable width is generated;

c. means for generating a reference voltage having a value dependent upon the spacing of said reference pulses in comparison to the duration of said control pulse; and

d. means for modifying the duration of the rectangular pulse of variable width following said first pulse as a function of the value of said reference voltage.

8. The combination set forth in claim 7 further including means for storing said reference voltage so that the duration of more than one pulse of variable width may be modified thereby.

9. The combination set forth in claim 7 further including:

a. means for generating a second rectangular control pulse in response to the termination of said first rectangular control pulse;

b. means for modifying the voltage level of said reference voltage in accordance with the duration of said second rectangular control pulse; and

c. means for modifying the duration of said pulse of variable width as a function of the modification in said voltage level, when the spacing between two reference pulses exceeds the pulse width of said first and second rectangular control pulses.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 3,651,3 5 Dated March 21, 1972 Inventor(s) Louis A. Monpetit It'is certified that error appears in the above-identified patenand that said Letters Patent are hereby corrected as shown below:

In column 3, line ll,"l should be T In column 3, line #5, "I should be T 7 Column 3, line "(l that, should be (T It is clear that, 3

Column 3, line 63, "R should be R i Column 3, line 6 "13 should be D Column A, line 40, "15" should be T Column 4, line 75, after '.'being" insert momentarily Column 5, line 50, "articular" should be particular Column '7 line 31 "I should be T Column 7, line 32 "I 'f should be 'I' Signed and sealed this 3rd day of October 1972.

(SEAL) Attes't:

EDWARD M.FLDTCHER,JH. ROBERT GOTTSCHALK Attestlng Officer Commissioner of Patents FORM (1069) USCOMM-DC 60376-1 69 9 Us, GOVERNMENT PRINTING OFFICE 19" OSGQH 

1. A method of controlling the width of a rectangular pulse in response to a series of reference pulses of variable spacing, comprising the steps of: a. generating a first pulse of variable width commencing with a pulse in said series of reference pulses; b. generating a rectangular control pulse of predetermined duration commencing with said pulse in said series of reference pulses; c. generating a reference voltage, the voltage level of which is dependent upon the spacing of said reference pulses in comparison to the duration of said control pulse; and d. modifying the duration of said first pulse as a function of the voltage level of said reference voltage.
 2. The method set forth in claim 1 wherein said reference voltage is generated in response to the termination of said control pulse.
 3. The method set forth in claim 2 wherein said reference voltage is generated from an initial level, linearly up to a predetermined maximum level when the spacing of said reference pulses bears a predetermined relationship to the width of said control pulse and up to a value lower than said predetermined maximum level when the spacing of said reference pulses varies from said predetermined relationship.
 4. The method set forth in claim 3 including the further step of returning said reference voltage to said initial level in response to the termination of a second pulse of variable width generated after said first pulse.
 5. The method set forth in claim 1 wherein the duration of said rectangular control pulse is greater than the spacing between two pulses in said series of reference pulses and further including the step of storing said reference voltage for modifying the duration of at least two pulses of variable width.
 6. The method set forth in claim 1 further including the steps of: a. generating a second rectangular control pulse of predetermined duration in response to the termination of said first rectangular control pulse; b. modifying the voltage level of said reference voltage in accordance with the duration of said second rectangular control pulse; and c. modifying the duration of said first pulse of variable width in accordance with the modification in said voltage level when the spacing between two reference pulses exceeds the pulse widths of said first and second rectangular control pulses.
 7. A circuit for modifying the width of a rectangular pulse in response to a series of reference pulses of variable spacing, comprising: a. means responsive to a reference pulse in said series of reference pulses for generating a first pulse of variable width; b. means for generating a rectangular control pulse of predetermined duration at the same time said first pulse of variable width is generated; c. means for generating a reference voltage having a value dependent upon the spacing of said reference pulses in comparison to the duration of said control pulse; and d. means for modifying the duration of the rectangular pulse of variable width following said first pulse as a function of the value of said reference voltage.
 8. The combination set forth in claim 7 further including means for storing said reference voltage so that the duration of more than one pulse of variable width may be modified thereby.
 9. The combination set forth in claim 7 further including: a. means for generating a second rectangular control pulse in response to the termination of said first rectangular control pulse; b. means for modifying the voltage level of said reference voltage in accordance with the duration of said second rectangular control pulse; and c. means for modifying the duration of said pulse of variable width as a function of the modification in said voltage level, when the spacing between two reference pulses exceeds the pulse width of said first and second rectangular control pulses. 